Diagnostics of rotating components are a maturing field. Various studies have disclosed a number of analysis techniques for monitoring rotating components, such as synchronous analyses (primarily for shafts and gears) and non-synchronous analyses (primarily for bearings). Synchronous analysis is based on a time synchronous average (TSA) so as to eliminate signal components that are not synchronous with the rate of rotation of the shaft or gear, whereas non-synchronous analyses generally use some type of demodulation and enveloping, returning the energy associated with the fault frequency of the item under analysis (e.g., bearing).
For shaft/gear analyses, a further analysis of the TSA is typically performed to give an indication of the condition of the object under surveillance. These other analyses can be a statistic of the time domain waveform (e.g., TSA root mean square (RMS), TSA Kurtosis, RMS of the TSA residual signal), statistics based on time and frequency domain waveforms (e.g., Figure of Merit (a quantity used to characterize the performance of a device, system or method, relative to its alternatives) 0, in which the TSA peak to peak is divided by gear mesh energies), or the frequency domain itself (first harmonic of the shaft speed, which is called the shaft order 1 magnitude). Whether from synchronous or non-synchronous analysis, these statistics are typically called “condition indicators” (CIs), which can be used to understand the diagnostics of the component under analysis.
In certain instances, the original equipment manufacturer (OEM) may have set nonconformity limits for some components (e.g., 1 inch per second on the shaft order 1 magnitude, for example), to define when maintenance should be performed. However, most components have no formal limits and therefore, the operator or a health and usage monitoring system (HUMS) vendor is left to define component nonconformity thresholds.